Production of isoprene.



ARTHUR HEINEMANN, OF WEST KENSINGTON, LONDON, ENGLAND.

PRODUCTION OF ISOPRENE.

Specification of Letters latent.

Patented Nov. 9, 1915.

No Drawing. Original application filed June 9, 1911, Serial No. 632,202. Divided and this application filed 4 March 13, 1914, Serial No. 824,384.

To all whom it may concern:

Be it known that I, ARTHUR HEINEMANN, a subject of the King of Prussia, residing at 223 North End road, West Kensington, London, W., England, formerly at 10 Sumner- This invention consists of improvements in the production of isoprene by the depolymerization of turpentine oil.

The improvements described herein are analogous to the improvements described in the specification of my U. S. A. application Serial No. 632,202, filed on June 9th 1911, from which this application has been divided. Up to the present time the depolymerization of turpentine oil has been elfected by bringing the vapors of said oil into contact with heated iron. This method of producing isoprene was adopted by Sir William Tilden who passed the turpentine oil through an iron tube heated to a dull red heat. The yield of isoprene so obtained was very small, being about 6.25 per cent. of the turpentine oil used.

More recently it has been proposed to obtain isoprene by passing vapors of turpentine oil through an iron tube heated to a temperature of between 550 C. and 660 0., and filled with rolls of iron, or wire, gauze or perforated disks formed of iron.

The object of my invention is to obtain a greater yield of isoprene than has hitherto been possible.

According to my invention I use silver, instead of iron, as a catalytic or contact substance. I have found that this metal possesses the important advantage, probably due to its more highly conductive nature, of allowing the isoprene to be produced at a lower temperature than when iron is employed.

The silver must either be in a. finely divided state, in which case it would be contained in a tube of iron or other suitable material, or must form the substance of which is constructed the tube or structure in which the depolymerization of the turpentine oil is efiected. Said tube or structure may be of any suitable form. For instance it may consist of a helical, spiral or zig-zag tube, or of a box provided with a series of baflie plates so disposed with respect to one another that the vapor of the turpentine oil is compelled to travel in a sinuous path.

In order to obtain the maximum yield of isoprene and prevent the isoprene being converted into dipentene, the depolymerization should be eflected at as low a temperature as possible and the rate of flow and length of pipe so adjusted that polymerization of the isoprene 1s prevented as far as possible. It

is advisable to connect the delivery tube to a condenser of suitable size, which is preferably cooled by a freezing mixture.

The invention may be carried out in the following manner :The vapor of turpentine oil is passed through or over the heated silver at the lowest temperature which is found to work satisfactorily. This temperature, if there is an ample surface exposed to the vapor, is about 450 C. Good results may be obtained if a tube of 6 millimeters internal diameter and 4 meters in length is closely wound into a coil and the rate of flow of the vapor through said coil isregulated so as to be equal to or approximately equal to 2.000 cubic centimeters per hour. As a result of the depolymerization of the turpentine oil isoprene and a number of other hydrocarbons are produced, equal to about per cent. by volume of the quantity ofthe turpentine vapor. The isoprene, which can be readily separated from the other hydrocarbons by distillation, will be found to be about 25' per cent. of the original volume of turpentine oil.

Having now described my invention what I have invented and desire to secure by Letters Patent of the United States is as follows 1. A process for the production of isoprene from turpentine oil consisting in passing the vapors of turpentine oil over heated In testimony whereof I have signed my silyer, substantially as described. name to this specification in the presence.

2. A process for the production of isoof two subscribing Witnesses. prene from turpentine oil consisting in pass- ARTHUR HEINEMANN. 5 ting the vapors of turpentine oil through a Witnesses:

heated structure of suitable form made of ARTHUR F. ENNIS,

silver, substantially as described. W. E. ROGERS. 

